A Stack is a container-type component that abstracts the implementation of a flexbox in order to define the layout of its children components.

Stack Properties

Although the Stack component has a number of different properties, there are three in particular that define the overall layout that the component has:

  1. Direction: Refers to whether the stacking of children components is horizontal or vertical. By default the Stack component is vertical, but can be turned horizontal by adding the horizontal property when using the component.

  2. Alignment: Refers to how the children components are aligned inside the container. This is controlled via the verticalAlign and horizontalAlign properties. One thing to notice here is that while flexbox containers align always across the cross axis, Stack aims to remove the mental strain involved in this process by making the verticalAlign and horizontalAlign properties always follow the vertical and horizontal axes, respectively, regardless of the direction of the Stack.

  3. Spacing: Refers to the space that exists between children components inside the Stack. This is controlled via the gap and verticalGap properties.

Stack Items

The Stack component provides an abstraction of a flexbox container but there are some flexbox related properties that are applied on specific children of the flexbox instead of being applied on the container. This is where Stack Items comes into play.

A Stack Item abstracts those properties that are or can be specifically applied on flexbox's children, like grow and shrink.

To use a Stack Item in an application, the Stack component should be imported and Stack.Item should be used inside of a Stack. This is done so that the existence of the Stack Item is inherently linked to the Stack component.

Stack Wrapping

Aside from the previously mentioned properties, there is another property called wrap that determines if items overflow the Stack container or wrap around it. The wrap property only works in the direction of the Stack, which means that the children components can still overflow in the perpendicular direction (i.e. in a Vertical Stack, items might overflow horizontally and vice versa).

Stack Nesting

Stacks can be nested inside one another in order to be able to configure the layout of the application as desired.

For more details and examples visit the official docs. The R package can not handle each and every case, so for advanced use cases you need to work using the original docs to achieve the desired result.





'auto' | 'stretch' | 'baseline' | 'start' | 'center' | 'end'
Defines how to align the StackItem along the x-axis (for vertical Stacks) or the y-axis (for horizontal Stacks).


Defines a CSS class name used to style the StackItem.


number | string
Defines order of the StackItem.


boolean | number | 'inherit' | 'initial' | 'unset'
Defines at what ratio should the StackItem shrink to fit the available space.


Defines how to render the Stack.


Defines whether Stack children should not shrink to fit the available space.


number | string
Defines the spacing between Stack children. The property is specified as a value for 'row gap', followed optionally by a value for 'column gap'. If 'column gap' is omitted, it's set to the same value as 'row gap'.


boolean | number | 'inherit' | 'initial' | 'unset'
Defines how much to grow the Stack in proportion to its siblings.


Defines whether to render Stack children horizontally.


Defines how to align Stack children horizontally (along the x-axis).


number | string
Defines the maximum height that the Stack can take.


number | string
Defines the maximum width that the Stack can take.


number | string
Defines the inner padding of the Stack.


Defines whether to render Stack children in the opposite direction (bottom-to-top if it's a vertical Stack and right-to-left if it's a horizontal Stack).


Defines how to align Stack children vertically (along the y-axis).


Defines whether the Stack should take up 100% of the height of its parent. This property is required to be set to true when using the grow flag on children in vertical oriented Stacks. Stacks are rendered as block elements and grow horizontally to the container already.


Defines whether Stack children should wrap onto multiple rows or columns when they are about to overflow the size of the Stack.



if (interactive()) {
    ui = Stack(
      tokens = list(childrenGap = 10),
      reversed = TRUE,
      span("Item One"),
      span("Item Two"),
      span("Item Three")
    server = function(input, output) {}